Marumo rules as king of the fairy world, specifically known as the Muglox World. He is the father of the main fairy characters, Mirumo and Murumo. Governing by strict laws, he enforces the crucial mandate that fairies must return to their home world immediately after their human partner's wish is granted. He personally delivers this ultimatum to Mirumo via holographic call, imposing a strict one-hour countdown for compliance to avoid severe, unspecified punishment, emphasizing that no fairy has ever broken this rule.

His royal authority encompasses significant duties, such as originally arranging Mirumo's engagement to Princess Rima before Mirumo fled to the human world. Marumo's leadership proves vital during a crisis where magical interference threatens to freeze the fairy world in time, requiring collective action to restore balance. As royalty, he holds the power to authorize transformative magic, including temporarily turning humans into fairies.

Interactions with his sons reveal his temperament. He visibly loses composure, shouting to regain attention when Mirumo interrupts or ignores him during their holographic exchange. Their dynamic features comedic tension, like Mirumo's thwarted desire to physically smack his intangible holographic father. Beyond rule enforcement, Marumo fulfills ceremonial roles, officiating Mirumo and Rima's wedding at the manga's conclusion.